I am considering printing a book featuring the best of my one-panel "Pen Grenades" comics, and this article caught my eye. It's from Publishers Weekly on the subject of more affordable print-on-demand books.
The company is Ingram, and their P.O.D. branch is called Lightning Source.
I haven't heard much about the print quality, except one customer who believes that the difference between their "normal" and "premium" printing is the paper weight: 50 lb vs. 70 lb.